Fixel-Based Analysis of White Matter Alterations in Facial Palsy

Predicting individual prognosis is difficult despite various risk factor studies, due to the complex recovery involving peripheral nerve restoration and cerebral plasticity. This study uses fixel-based analysis (FBA) to better understand neural pathway alterations, hypothesizing that FBA can effectively link functional outcomes with diffusion metrics in the process of rehabilitation. The authors recruited 50 participants including 30 patients and 20 healthy controls into the study. All of them underwent assessment 3 months and 6 months after injury. Both whole-brain fixel-based analysis and tract of interest analysis were performed. The authors observed multiple regions including the superior corona radiata, posterior limb of the internal capsule, and cerebral peduncle displaying significant changes of FD (fiber density), FC (fiber-bundle cross-section), and FDC (fiber density and cross-section). Patients with unfavorable outcomes showed increased FD in the ipsilesional side and decreased FD in the contralesional side compared with patients with favorable outcomes. In addition, FD values of the contralesional side exhibited positive correlations with differences in FGS at 3 months and 6 months. Conversely, FD values in the ipsilesional side showed a negative correlation. Our findings suggest that FD metrics within the corticobulbar tract could serve as predictive biomarkers for symmetry outcomes. Thus, FBA holds promise for early estimation of behavioral outcomes in facial palsy, guiding more targeted interventions.